The conventional door hinge is composed of two leaves each engaging with the other by pivot and sleeve. One leaf is fixed on the door edge and the other is fixed on the door frame. It plays the role for pivotting the door when opening or closing the door. For automatically closing the door with conventional hinge, a hydraulic system means may be used for this purpose. Said automatic door closing means of hydraulic system is provided on the upper portion of door and on the horizontal beam of the upper door frame. The hydraulic door closing means will exert a great resisting force so that a big force should be applied to push the door whenever opening the door. Said closing means is provided on the upper portion of the door. The door opening force is unhomogeneous. The door will thus be easily deformed or damaged. Said heavier door system is used for bigger steel door or aluminum door. It is not suitable for general wooden door. Its structure is complicated and not economic for wider applications.
Another automatic door closing means is made of spring which is fixed on the upper portion of door near hinge pivot and the frame. The spring will lose its resilient effect after long time service and will affect the door for incomplete closing. It is also used for small door or window and is not suitable for heavier door.